Renin is a proteolytic enzyme produced and secreted into the bloodstream by the juxtaglomerular cells of the kidney. In the bloodstream, renin cleaves a peptide bond in the serum protein angiotensinogen to produce a decapeptide known as angiotensin I. A second enzyme known as angiotensin converting enzyme, cleaves angiotensin I to produce the octapeptide known as angiotensin II. Angiotensin II is a potent pressor agent responsible for vasoconstriction and elevation of cardiovascular pressure. Attempts have been made to control hypertension by blocking the action of renin or by blocking the formation of angiotensin II in the body with inhibitors of angiotensin I converting enzyme.
Classes of compounds published as inhibitors of the action of renin on angiotensinogen include renin antibodies, pepstatin and its analogs, phospholipids, angiotensinogen analogs, pro-renin related analogs and peptide aldehydes.
A peptide isolated from actinomyces has been reported as an inhibitor of aspartyl proteases such as pepsin, cathepsin D and renin [Umezawa et al, in J. Antibiot. (Tokyo), 23, 259-262 (1970 )]. This peptide, known as pepstatin, was found to reduce blood pressure in vivo after the injection of hog renin into nephrectomized rats [Gross et al, Science, 175, 656 (1971 )]. Pepstatin has the disadvantages of low solubility and of inhibiting acid proteases in addition to renin. Modified pepstatins have been synthesized in an attempt to increase the specificity for human renin over other physiologically important enzymes. While some degree of specificity has been achieved, this approach has led to rather high molecular weight hepta- and octapeptides [Boger et al, Nature, 303, 81 (1983 )]; high molecular weight peptides are generally considered undesirable as drugs because gastrointestinal absorption is impaired and plasma stability is compromised.
Short peptide aldehydes have been reported as renin inhibitors Kokubu et al. Biochim. Biophys. Res. Commun., 118, 929 (1984 ); Castro et al. FEBS Lett., 167, 273 (1984 )]. Such compounds have a reactive C-terminal aldehyde group and would likely be unstable in vivo.
Other peptidyl compounds have been described as renin inhibitors. EP Appl. #128,762, published 18 December 1984, describes dipeptide and tripeptide glycol-containing compounds as renin inhibitors [also see Hanson et al. Biochim. Biophys. Res. Commun., 132, 155-161 (1985 ), 146, 959-963 (1987 )]. EP Appl. #181,110, published 14 May 1986, describes dipeptide histidine derivatives as renin inhibitors. EP Appl. #189,203, published 30 July 1986, describes alkylnaphthyl-methylpropionyl-histidyl aminohydroxy alkanoates as renin inhibitors. EP Appl. #216,539, published 1 April 1987, describes alkylnaphthylmethylpropionyl aminoacyl aminoalkanoate compounds as renin inhibitors orally administered for treatment of renin-associated hypertension. EP Appl. #229,667 published 22 July 1987 describes acyl a-aminoacyl aminodiol compounds having a piperazinylcarbonyl or an alkylaminoalkylcarbonyl terminal group at the N-amino acid terminus, such as 2 (S)-{[(1-piperazinyl)-carbonyl]-oxy]-3-phenylpropionyl}-Phe-His amide of 2 (S)-amino-1-cyclohexyl-3 (R),4 (S)-dihydroxy-6-methylheptane. PCT Application No. WO 87/04349 published 30 July 1987 describes aminocarbonyl aminoacyl hydroxyether derivatives having an alkylamino-containing terminal substituent and which are described as having renin-inhibiting activity for use in treating hypertension. EP Appl. #300,189 published 25 January 1989 describes amino acid monohydric derivatives having an alkylamino-alkylamino N-terminus which are mentioned o as useful in treating hypertension. EP Appl. #266,950 published 5 November 1988 describes heterocycliccarbonyl amino acid derivatives which are mentioned as having renin-inhibiting activity for use in treating hypertension.